Present knowledge of the structure and physiology of sensilla and their sensory neurons in the antennae of insects provide a basis for a detailed neurophysiological, anatomical, and ultrastructural study of neural pathways subserving olfaction and mechanosensation in the insect brain. This research aims to trace the pathways of antennal afferent axons into the central nervous system; to characterize the electrophysiological responses of the neurons in the deutocerebrum to defined olfactory and mechanosensory antennal inputs; to prepare an inventory of types and projections of deutocerebral neurons; to classify synapses in the glomeruli of the deutocerebral antennal lobes on the basis of ultrastructure and the cellular elements participating in each type; to probe further the chemical composition and physiological actions of male and female pheromone systems; and to test the usefulness of methods of metabolic cell-marking to construct functional maps of neural activity in the central nervous system with various types of antennal stimulation. These studies will employ the large, easily reared, and experimentally tractable lepidopteran insect Manduca sexta. The central effort in this work will involve intracellular recording of synaptic and action potentials in, and intracellular dye-marking of, deutocerebral neurons with glass microelectrodes in order to correlate cell responses with cell types. This research is expected to contribute knowledge about the brain mechanisms underlying olfactorily mediated behavior in insects and thereby to aid progress toward new and selective means of controlling insects that spread diseases and destroy food supplies.